1. Field of the Invention
The present invention relates to an exercising device or system, and more particularly to such a device or system using hydraulic means as a force resisting component.
2. Prior Art and Invention
The advantage of a hydraulic exercise machine are numerous and have been extensively cited in many previous patents as are the advantages of the various modes of exercising. The advantage of the combination of exercise modes (isodynamic and isokinetic) is explained further in the cross reference.
There are a number of prior art hydraulic exercise devices generally speaking similar in one respect or another to the type disclosed. However, there are none which are in combination as versatile, compact, smoothly operated and as easily constructed as the one disclosed. Most prior art hydraulic exercise devices use pumps with separate inlet and outlet ports, such as a hydraulic cylinder with a piston and hydraulic fluid on both sides of the piston. The two port type of design results in increase product cost over the single port design because of the required increase in the number of hydraulic circuit components, sliding seals, and precision machined surfaces. The performances of these machines are also degraded by the total increase in frictional seal resistance as a result of the extra seals.
Some prior art hydraulic exercise devices require careful balancing between two independent hydraulic circuits which is a difficult and tedious operation. The use of two hydraulic circuits in the design is also costly since it requires duplicating the components of a one circuit design.
Other prior art hydraulic exercise devices use more than one pump for the exercise machine. These devices are not only more expensive, but those, which use two or more hydraulic pumps that are basically mechanically independent and require load sharing for smooth exercising, run into trouble with differential seal friction among the pumps. This results in uneven operation and possible jamming of the exercise machine. An example of these exercise machines are the ones which use two hydraulic cylinders with a connecting bar for barbell type exercises.
Other prior art hydraulic exercise devices use a spring loaded relief valve for the isodynamic exercise mode. The device disclosed herein uses a weight loaded relief valve for the same purpose because of the psychological reinforcement of handling weights and because of the increase repeatability in obtaining a given level of exercise effort over a long term and from machine to machine.
The hydraulic exercise devices of the present invention by their inherent design eliminate the above mentioned shortcomings of the prior art. With the disclosed pump of the preferred embodiment only one sliding seal and seal surface is required and only one pump is required per machine, even if two mechanical outputs are required. Also, only one hydraulic circuit is required per machine. Jamming of the machine is completely eliminated by the design even with uneven loading. Also, the design of the hydraulic circuit is of minimum complexity since the hydraulic pump is single acting with a common inlet and outlet port.
A feature of the disclosed invention which it is believed is not available in any other exercise device is the combination of isokinetic and isodynamic modes. Many people who exercise with isokinetic machines get lulled into exerting a force which is somewhat less than their capacity. This is because the faster the isokinetic machine is worked, the greater the required force and vice versa. So, if a person is pyschologically down, he will tend to exert less by exercising slower which is easily done on an isokinetic machine. This shortcoming is eliminated by the combination of modes which sets a bottom limit to the exercise effort but allows any effort above the bottom limit to fluctuate in an isokinetic fashion. In this way the person exercising can set the isodynamic mode to something near his capacity, as this will prevent him from relaxing or working less than this setting. Also, most isokinetic machines have a dead band at the beginning of an exercise stroke and at the end of an exercise stroke. The dead band is the time or distance it takes to accelerate and deaccelerate the exercise machine to a point where meaningful exercising can be done. As a result the person exercising looses the very beginning and ending of an exercise movement. With the combination of modes in the present invention the dead band is nearly eliminated, since the machine will not move until the bottom limit of the exercise effort is exceeded.